Coma is a state of unconsciousness in which a person cannot be awakened; fails to respond normally to painful stimuli, light, or sound ; lacks a normal wake -sleep cycle; and does not initiate voluntary actions. A person in a state of coma is described as being comatose. A distinction is made in the medical community between a real coma and a medically induced coma; the former is a result of circumstances beyond the control of the medical community, while the latter is a means by which medical professionals may allow a patient 's injuries to heal in a controlled environment.
A comatose person exhibits a complete absence of wakefulness and is unable to consciously feel, speak, hear, or move. Clinically, a coma can be defined as the inability to consistently follow a one-step command. It can also be defined as a score of ≤ 8 on the Glasgow Coma Scale lasting ≥ 6 hours. For a patient to maintain consciousness, two important neurological components must function. The first is the cerebral cortex—the gray matter that forms the outer layer of the brain. The other is a structure located in the brainstem, called reticular activating system (RAS).Injury to either or both of these components is sufficient to cause a patient to experience a coma. The cerebral cortex is a group of tight, dense, " gray matter " composed of the nuclei of the neurons whose axons then form the " white matter," and is responsible for perception, relay of the sensory input via the thalamic pathway, and many other neurological functions, including complex thinking.
